Coronavirus concentrations in wastewater across the country have risen significantly, signaling a continuation of the summer surge.
Measurements of the virus in U.S. wastewater reached “high” levels for the first time this summer, according to estimates released Friday by the Centers for Disease Control and Prevention, which reported that COVID-19 cases are increasing or possibly increasing in 44 states and the nation’s capital.
And for the first time since the winter, CDC data for the week ending July 6 found that California has “very high” coronavirus concentrations in its wastewater. California is one of seven states in that category — the others are Arkansas, Florida, Maryland, Nevada, Oregon, and Texas. Nineteen other states, covering every region of the country, have high coronavirus concentrations in their wastewater.
Concentrations of coronavirus in California’s wastewater are now estimated to be significantly higher than they were last summer, and in Northern California, two of the largest wastewater treatment plants serving San Jose and Palo Alto in Santa Clara County (the region’s most populous county) have reported high concentrations of the virus in wastewater.
And the percentage of COVID-19 tests coming back positive in California is nearly at its peak from last summer. In the week ending July 8, 13% of reported test results were positive, up from 4.8% in the same week a month earlier. The latest positivity rate is nearly above last summer’s peak of 13.1% in late August and early September.
Los Angeles County, the most populous county in the nation, has seen a significant increase in coronavirus concentrations in wastewater.
Additionally, the Los Angeles County Department of Public Health said in a statement to the Times that the county is “seeing an increase in COVID-19 cases, emergency department visits and hospitalizations. It remains to be seen whether we will see a larger wave of infections this summer compared to last summer.”
According to the health department, in the 10 days ended June 29, the most recent available period, coronavirus concentrations in Los Angeles County wastewater were 27% of last winter’s peak, a significant increase from the previous same period ended June 22, when levels were 17% of last winter’s peak.
The county’s COVID-19 case numbers have also been surging: The average number of new cases per day was 307 for the week ending July 7, up from 121 the previous month. The peak last summer was a daily average of 571 for the week ending Aug. 26.
Officially reported cases are certainly an undercount because they reflect only tests done in health care facilities, not tests done at home. Moreover, fewer people get tested for COVID when they are sick. But measuring the number of infected people is still useful in assessing overall trends.
The rate of coronavirus-related emergency room visits in Los Angeles County is also rising. In the week ending July 7, 2.5% of emergency room visits were coronavirus-related. A month earlier, that figure was down to 1.5%. The peak last summer was in the week ending August 27, when 5.1% of emergency room visits were coronavirus-related.
The mid-year increase in COVID-19 cases began in May and arrived earlier than normal. Previously, Los Angeles County’s mid-year increases in cases and hospitalizations began in early July in 2021 and 2023, but in early May in 2022.
Kaiser Permanente Southern California Hospital continues to see an increase in cases, primarily among outpatients, officials said.
“We’re still seeing a slow, slow increase in cases,” said Dr. Elizabeth Hudson, regional director of infectious diseases for Kaiser Southern California. “We’ll have to wait and see what happens, because we’re past the Fourth of July, and if we’re going to see an increase in cases, that’s usually when we’re going to see it.”
Health officials across the U.S. are closely monitoring the rise in cases. The New York City Department of Health and Mental Hygiene on Tuesday urged residents to consider wearing masks, especially in crowded indoor spaces, as cases are on the rise, especially if they are at high risk. “New York City, wear a mask!” the department said in a social media post, along with illustrations of passengers wearing masks on public transportation.
The rise in coronavirus cases comes with the rise of a new variant called FLiRT that is estimated to be 20% more transmissible than the winter variant that dominates. In the two weeks ending July 6, an estimated 70.5% of coronavirus samples nationwide were of the FLiRT variant, officially known as KP.3, KP.2 and KP.1.1. This is up from 54.9% a month earlier.
The CDC has not identified any states where COVID-19 cases are declining or appear to be declining over the summer. Three states — Hawaii, New Mexico and Oregon — have stable or uncertain COVID-19 case counts, according to the CDC. Estimates were not available for Missouri, Wisconsin or Wyoming.